This invention relates to chemical mechanical polishing.
Chemical mechanical polishing is one technique utilized to process the outer surface of one or more layers formed over a semiconductor wafer. One principal use of chemical mechanical polishing is to render an outer wafer surface of a layer or layers of dielectric material to be more planar than existed prior to starting the polishing. Only some or all of the outermost layer being polished might be removed during such a process.
In chemical mechanical polishing, typically both the wafer and the pad which polishes the wafer are caused to rotate during the polishing action, typically in opposite directions. A liquid slurry is received intermediate the wafer and the polishing pad. The slurry comprises a liquid solution, typically basic, and a solid grit material, typically particles of a substantially consistent size (i.e., within 5 nanometers of the size selected from around 25 to 100 nanometers in diameter). The action of the liquid solution and grit within the solution intermediate the wafer and pad imparts removal of outer wafer layers utilizing both chemical and mechanical actions.
Although it is the intent of chemical mechanical polishing and other planarization processes to planarize a layer essentially completely flat, undesired finished topography can result depending upon the polishing conditions, the slurry and the materials being polished. It would be desirable in most instances to reduce the degree of residual topography remaining at the conclusion of a chemical mechanical polishing planarization process.
In one implementation, a chemical mechanical polishing method includes providing a workpiece having a dielectric region to be polished. A first chemical mechanical polishing of the dielectric region is conducted on the workpiece using a polishing pad and a first slurry. Then, a second chemical mechanical polishing is conducted of the dielectric region on the workpiece using the polishing pad and a second slurry different from the first slurry.
In one implementation, a chemical mechanical polishing method includes providing a workpiece having a dielectric region to be polished. The dielectric region has a thickness ultimately desired to removed by polishing prior to moving the workpiece on to a subsequent nonpolishing processing step. A first chemical mechanical polishing of the dielectric region is conducted on the workpiece using a first slurry. Then, a second chemical mechanical polishing of the dielectric region is conducted on the workpiece using a second slurry different from the first slurry. The second chemical mechanical polishing removes at least 15% of the thickness.